June 26, 2014 -- Final

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Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes for CFC-12, HCFC-22 and R-502 in Vending Machines

Substitute: Propane (R-290)

This risk screen is restricted to vending machines meeting the requirements of UL 541: 

Refrigerated Vending Machines.

This risk screen does not contain Clean Air Act (CAA) Confidential Business Information (CBI) 

and, therefore, may be disclosed to the public.

1. INTRODUCTION

Ozone-depleting substances (ODS) are being phased out of production in response to a series of 

diplomatic and legislative efforts that have taken place over the past two decades, including the Montreal 

Protocol and the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection 

Agency (EPA), as authorized by Section 612 of the CAAA, administers the Significant New Alternatives 

Policy (SNAP) Program, which identifies acceptable and unacceptable substitutes for ODS in specific 

end-uses based on assessment of their health and environmental impacts. 

EPA’s decision on the acceptability of a substitute is based on the findings of a screening assessment of 

potential human health and environmental risks posed by the substitute in specific applications. EPA has 

already screened a large number of substitutes in many end-use applications within all of the major ODSusing sectors including: refrigeration and air conditioning, solvent cleaning, foam blowing, aerosols, fire 

suppression, adhesives, coatings and inks, and sterilization. The results of these risk screens are presented 

in a series of Background Documents that are available in EPA's docket.

The purpose of this risk screen is to supplement EPA’s Background Document on the refrigeration and air 

conditioning sector (EPA 1994) (hereinafter referred to as the Background Document). This risk screen 

evaluates the potential use of propane as a substitute for CFC-12, HCFC-22, and R-502 in the vending 

machine end-use. Table 1 presents the composition of the proposed substitute, including the estimated 

concentrations of impurities, which may be present in the proposed substitute.

Table 1. Composition of Propane

Component Chemical Formula CAS Number Concentration

(Weight Percent)

Proposed Substitute

Propane C3H8 74-98-6 99.5%

Potential Impurities (maximum concentration)

Ethane C6H14 74-84-0 0.17%

Propylene C3H6 115-07-1 0.03%

n-Butane C4H10 106-97-8 0.1%

Sulfur S 7704-34-9 0.001%

Water H2O 7732-18-5 0.0012%

 

Section 2 summarizes the results of the risk screen for the proposed substitute listed in Table 1. The

remainder of the risk screen is organized into the following sections:
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 Section 3: Atmospheric Assessment

 Section 4: Volatile Organic Compound Assessment 

 Section 5: Discussion of End-Use Scenario Modeled

 Section 6: Potential Health Effects

 Section 7: Flammability Assessment

 Section 8: Asphyxiation Assessment

 Section 9: End-Use Exposure Assessment 

 Section 10: Occupational Exposure Assessment

 Section 11: General Population Exposure Assessment

 Section 12: References

2. SUMMARY OF RESULTS

Propane is recommended for SNAP approval for vending machines that comply with Underwriters 

Laboratory (UL) Standard 541: Refrigerated Vending Machines. EPA's risk screen indicates that the use 

of the proposed substitute will be less harmful to the atmosphere than the continued use of CFC-12, 

HCFC-22, and R-502 as it is less harmful to the ozone layer, has lower climate impact, and a shorter 

atmospheric lifetime. Propane is subject to volatile organic compound (VOC) regulations under the CAA 

(40 CFR 51.100(s)). Based on analysis of potential impacts of hydrocarbon refrigerant emissions on 

ground-level ozone concentrations, VOC emissions from the use of propane in vending machines are not 

anticipated to contribute significantly to ground level ozone concentrations in the United States. No 

significant asphyxiation risks to consumers or toxicity risks to workers, consumers, or the general 

population are expected. It is expected that procedures identified in the material data safety sheet (MSDS)

for propane and good manufacturing practices will be adhered to, and that the appropriate safety and 

personal protective equipment (PPE) (e.g., protective gloves, tightly sealed goggles, protective work 

clothing, and suitable respiratory protection in case of leakage or insufficient ventilation) consistent with 

Occupational Safety and Health Administration (OSHA) guidelines will be used during manufacture, 

installation and servicing, and disposal of vending machines using propane. Because vending machines

are to be installed in locations with adequate space and/or ventilation in accordance with EPA 

recommendations and the equipment maintenance manual for propane, as discussed in greater detail in 

Section 9, significant toxicity or flammability risk to consumers is also unlikely. Additional safeguards, 

including specified refrigerant concentration limits (RCL) for propane, are also provided by adherence to 

industry standards including American Society of Heating, Refrigerating and Air-Conditioning Engineers 

(ASHRAE) Standards 15,

1

34,

2

and 623and Underwriters Laboratory (UL) Standard 541, Supplement 

SA.4

3. ATMOSPHERIC ASSESSMENT

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of 

propane in vending machines. The ozone depletion potential (ODP), global warming potential (GWP), 

and atmospheric lifetime (ALT) of the proposed substitute are presented in Table 2.

 

1

Safety Standard for Refrigeration Systems ASHRAE Standard 15 establishes safeguards for life, limb, health, and property and 

prescribes safety requirements.

2 Designation and Safety Classification of Refrigerants ASHRAE Standard 34 is establishes a uniform system for assigning 

reference numbers, safety classifications, and refrigerant concentration limits to refrigerants. Safety classifications based on 

toxicity and flammability data are included.

3 Ventilation for Acceptable Indoor Air Quality ASHRAE Standard 62 establishes minimum ventilation rates and other measures 

intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects.

4 UL 541: Refrigerated Vending Machines Supplement SA: Requirements for Refrigerated Venders Employing a Flammable 

Refrigerant in the Refrigerating System
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The proposed substitute is substantially less harmful to the ozone layer, has lower climate impact, and a 

shorter atmospheric lifetime when compared to CFC-12, HCFC-22, and R-502. In addition, propane also 

has lower climate impact and a shorter atmospheric lifetime than those predicted for other substitutes 

examined in the Background Document, as well as commonly utilized substitutes R-404A and HFC-134a.

Thus, EPA believes that the use of propane would result in substantially less harm to the climate and 

ozone layer than the continued use of ODS and commonly used ODS substitutes.

Table 2. Atmospheric Impacts of Propane Compared to Other Vending Machine Refrigerants

Refrigerant ODPa GWPb ALT (Years)

Propane 0 3.3 0.03a

CFC-12 0.82 10,900 100b

R-502c 0.2 4,650 NAd

HCFC-22 0.05 1,810 12b

R-404Ae 0 3,920 NAf

HFC-134a 0 1,430 14b

NA= Not Available.

a WMO 2010 Scientific Assessment Report (2011).

b

IPCC 4th Assessment Report (Forster et al. 2007).

c R-502 is a blend consisting of HCFC-22 (49%) and CFC-115 (51%). 

d Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HCFC-22 is 12 years and 

the ALT for CFC-115 is 1,700 years (IPCC 4th Assessment Report [Forster et al. 2007]).

e R-404A is a blend consisting of HFC-143a (52%), HFC-125 (44%) and HFC-134a (4%). 

f Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HFC-143a is 52 years, the 

ALT for HFC-125 is 29 years, and the ALT for HFC-134a is 14 years.

4. VOLATILE ORGANIC COMPOUND ASSESSMENT

Propane is regulated as a VOC under CAA regulations (40 CFR 51.100 [s]). Through regulations and 

standard industry practices, VOC emissions should be controlled. A separate analysis was prepared by 

EPA (2014) to evaluate the potential impact of the use of hydrocarbon refrigerants on ground-level ozone 

concentrations in the United States. The analysis estimated refrigerant emissions from refrigeration and 

air conditioning equipment, which were assumed to contain propylene, isobutane, and/or propane 4under 

different scenarios. Under the most conservative scenario, it was assumed that propylene was used in all 

refrigeration and air conditioning equipment. In the most realistic scenario, all three hydrocarbons were 

assumed to be used in certain types of refrigeration and air conditioning equipment, depending on the 

proposed use of each alternative under submissions received by the SNAP Program at the time of the 

analysis. End-uses in the evaluation included a number of types of smaller, self-contained refrigeration 

and room air-conditioning units for which SNAP hydrocarbon applications have been received and/or UL 

Standards covering flammable refrigerants exist. The hydrocarbon emissions from these scenarios were

estimated based on U.S. EPA’s Vintaging Model, and their potential contributions to ozone 

concentrations were assessed using U.S. EPA’s Community Multiscale Air Quality (CMAQ) model. 

CMAQ modeling was performed for April through the end of September, as these months presented the 

largest releases of hydrocarbon refrigerant as well as weather conditions favorable for ozone 

formation. The ozone concentrations were estimated for the Atlanta, Houston and Los Angeles regions, 

due to their distinctive geographic setting and chronic high levels of ground level ozone, and then scaled 

for national emission estimates. The results of the CMAQ modeling indicated that under the most realistic 

scenario, hydrocarbon refrigerants could potentially increase the maximum 8-hour average ground level 

ozone by no more than 0.15 ppb in Los Angeles, the city with the greatest ozone problem. This is roughly

0.2 percent of the current National Ambient Air Quality Standard (NAAQS) for ozone of 75 ppb. In the 

 

4 EPA uses the maximum incremental reactivity (MIR) of ethane (0.28 g-O3

/g-substance) as the threshold for determining 

whether a compound has negligible reactivity. Propylene (MIR = 11.57), isobutane (MIR = 1.34), and propane (MIR = 0.56) are 

all considered to be reactive compounds and are therefore subject to VOC regulations.
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most conservative case, where it was assumed that the most reactive hydrocarbon, propylene, was used in 

all refrigeration and air conditioning equipment, there could be an incremental increase of the 8-hour 

average as high as 6.61 ppb ozone, or an increase of up to 9 percent of the NAAQS. However, this upper 

bound level of increase is not likely, as most ozone nonattainment areas are not VOC-limited (i.e., the 

formation of ozone in these areas are not limited by VOC emissions, but by other compounds such as 

nitrogen oxide [NOx]). In addition, the analysis assumed no use of VOC-exempt refrigerants which may 

be used in the refrigeration and air conditioning end-uses. Based on the results of this analysis, VOC 

emissions from the use of propane in vending machines are not anticipated to contribute significantly to 

ground-level ozone concentrations in the United States.

5. DISCUSSION OF END-USE SCENARIOS MODELED

Propane has been proposed for the vending machine refrigeration end-use. EPA expects that propane

vending machines will have a charge size of less than 150 grams, consistent with UL Standard 541: 

Refrigerated Vending Machines, which states that vending machines containing flammable refrigerants 

may have a charge size of up to 150 grams of A3 refrigerant. 

To represent a reasonable worst-case scenario, it is assumed that a catastrophic leak of refrigerant occurs 

while the vending machine is installed at the end-use. Because vending machines can be installed in a 

wide range of locations with varying room volumes, the analysis in this risk screen conservatively 

assumes that the vending machine contains the maximum charge size indicated by UL 541 (150 grams), 

and is located in the minimum room size, an enclosed alcove of a commercial building that can be 

isolated by a door. Under the worst-case scenario, the alcove is assumed to have an effective floor area of 

6.15 m2(i.e., excluding the space filled by the vending machine, furniture, boxes, etc.) and a height of 2.4 

meters), equivalent to a volume of 15 m3(530 ft3). Under the worst-case scenario, the full charge of the 

unit is assumed to be emitted over the course of one minute, into the enclosed alcove with 0.5 air changes 

per hour (ACH). A vertical concentration gradient is also assumed in the worst-case scenario since 

propane is denser than air (specific gravity of propane relative to air is 1.52 [air = 1]) and will settle in 

higher concentrations closer to the ground. In order to simulate the vertical concentration gradient, it is 

assumed that 95 percent of the leaked refrigerant mixes evenly into the bottom 0.4 meter of the room, and 

the rest of the refrigerant mixes evenly in the remaining volume (Kataoka 2000).

To represent a more typical scenario, this risk screen also evaluates potential risk associated with less 

conservative conditions. Based on ICF expert opinion, the enclosed alcove is assumed to have an 

effective floor area of 10m2(108ft3) with a height of 2.7 m (9 ft), equivalent to a volume of 27.5 m3(972 

ft3), with an air exchange rate of 1.5 ACH (EPA 1997). Additionally, because the typical breathing zone 

is above 0.4 meters (1.3 feet) and mixing is likely to occur upon release of propane from the unit because 

the system pressure is higher than the surrounding atmospheric pressure, a vertical concentration gradient

is not assumed. Table 3 details the end-use modeling assumptions used throughout the risk screen (i.e., in 

Sections 7, 8, and 9).

Table 3. End-Use Scenario Model Assumptions

Parameter Assumptions

Reasonable Worst-Case Scenario Typical Scenario

Room Type Enclosed Alcove Enclosed Alcove

Effective Size (m3)

a 15 (530 ft3

) 27.5 (972 ft3)

Ventilation Rate (air changes per hour) 0.5 1.5

Refrigeration Unit Vending Machine Vending Machine

Charge Size (g) 150 150

Length of Release (minutes) 1 1

Vertical Concentration Gradient Yes No

 a The volume of the room minus the volume occupied by the vending machine or other large pieces of equipment or furniture present.
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EPA recognizes that while the majority of vending machines may be placed outdoors or in other wellventilated areas, which would largely minimize the risks of exposure, there may a few instances in which 

the consumer chooses to place multiple vending machines in an enclosed space (thus further limiting the 

effective volume of the space) or chooses to place a single vending machine unit in a very small enclosed 

space (with the size of the vending machine being the limiting factor). A typical beverage vending 

machine measures 72 in x 39 in x 33 in, which is equal to 53.6 ft3or 1.5 m3(Vending Solutions 2009). To 

address these concerns, this risk screen incorporates threshold analyses in addition to the worst-case and 

typical scenario modeling. The results from the threshold analyses are used to establish guidelines for 

choosing an effective room size, charge size, and ventilation rate such that use of propane in vending 

machines does not present risk to consumers or servicing technicians. 

6. POTENTIAL HEALTH EFFECTS

To assess potential health risks from exposure to the proposed substitute in vending machines, EPA 

identified the relevant toxicity threshold values for comparison to modeled exposure concentrations for 

different scenarios. To protect consumers from the potential dangers of a catastrophic leak from the 

refrigeration unit, ASHRAE Standard 34 determined refrigerant concentration limits (RCLs) to reduce the 

risks of acute toxicity, asphyxiation, and flammability hazards in occupied spaces (ASHRAE 2010b). 

ASHRAE Standard 15 implements the aforementioned standard, requiring that “the concentration of 

refrigerant in an enclosed space following a complete discharge of a high-probability system shall not 

exceed the RCL” (ASHRAE 2010a). As such, this risk screen references the RCL in addition to the lower 

flammability limit, hypoxia No Observed Adverse Effect Level (NOAEL), and exposure limits, as an 

additional, conservative limit to ensure that significant flammability, asphyxiation, and end-use exposure 

risks, respectively, do not occur.

For the occupational exposure analysis, potential risks from chronic and acute worker exposure were 

evaluated by comparing exposure concentrations to available occupational exposure limits. Potential risks 

of chronic worker exposure were evaluated using workplace guidance levels (WGL). Risks from potential 

short-term consumer exposures were evaluated by comparing exposure concentrations to emergency 

guidance levels (EGL). In the absence of an established short-term exposure limit (STEL), acute exposure 

guidance levels (AEGLs), or an emergency response planning guideline (ERPG), potential short-term, 

end-use exposures of some of the impurities were compared to an excursion limit, which was calculated 

according to the methodology described in ACGIH (2004).5 Table 4 lists the relevant toxicity limits and 

RCLs of propane and its impurities, and is followed by Table 5, which provides an explanation of each 

toxicity limit. EPA’s approach for identifying or developing these values is discussed in Chapter 3 of the 

Background Document. 

 

5

It should be noted that this risk screen evaluates both short-term occupational and end-use (i.e., non-occupational) exposure to 

ethane and propylene by comparison to the excursion limit, which is typically used to evaluate short-term occupational exposure. 

EPA believes, however, that in the absence of an AEGL, STEL, or ERPG, the excursion limit provides a reasonable proxy. 

Notably, the ACGIH methodology (i.e., a calculation of three times the TLV-TWA) has also been used by DOE (2008) to

develop temporary emergency exposure limits (TEEL) for ethane (3,500 mg/m

3

or 2,900 ppm 15-min TWA) and propylene

(2,500 mg/m3 or 1,500 ppm 15-min TWA), which apply to the general population.
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Table 4. Exposure Limits of Propane and Potential Impurities

Component

8-hr WGL (Long-term 

Exposure)

ppm

EGL (Short-term Exposure)

ppm

Refrigerant Concentration 

Limit (RCL)

ppm

Propane 1,000a

(OSHA PEL)

10,000b,c (10 min AEGL-1)

6,900c(30 min AEGL-1) 5,300d

Potential Impurities

Ethane 1,000e (ACGIH TLV)

3,000f(30 min ACGIH Excursion 

Limit) 

2,900g(15-min TEEL-1)

7,000d

Propylene 500e(ACGIH TLV) 1,500f

(30 min ACGIH Excursion 

Limit) 1,000d

n-Butane 1,000e (ACGIH TLV) 6,900h (30 min AEGL-1) 4,000d

a OSHA PEL available at: http://www.cdc.gov/Niosh/npg/npgd0524.html

b An IDLH of 2,100 ppm has been established for propane. However, NIOSH (1996) states that "[b]ased on acute inhalation toxicity data in humans 

(ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been appropriate. However, the revised IDLH for propane is 2,100 

ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 2.1%)." Therefore, as this IDLH value is based on 

flammability concerns and not toxicity concerns, it is not used in the evaluation of toxicity risks in this risk screen.

c AEGL-1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf

d ASHRAE (2010b)

e ACGIH TLV for aliphatic hydrocarbon gases: alkane (C1 - C4) is 1,000 ppm TWA (ACGIH 2012) 

f Calculated as three times the TLV-TWA (ACGIH 2004).

g DOE (2008)

h AEGL-1 available at: http://www.epa.gov/oppt/aegl/pubs/rest102.htm

Table 5. Explanation of Exposure Limit-Related Terminologya

Organization Definition

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

ACGIH American Conference of Governmental Industrial Hygienists

AIHA American Industrial Hygiene Association

Exposure Limit Definition Explanation

Short-Term Exposure

RCL Refrigerant Concentration 

Limit

The RCL for a refrigerant is intended to reduce the risks of acute toxicity, 

asphyxiation, and flammability hazards in normally occupied, enclosed 

spaces. The RCL for each refrigerant is the lowest of the Acute-Toxicity 

Exposure Limit (ATEL), Oxygen Deprivation Limit (ODL), and Flammable 

Concentration Limit (FCL). Determination assumes full vaporization with 

no removal by ventilation, dissolution, reaction, or decomposition and 

complete mixing of refrigerant in the space to which it is released.

STEL Short-Term Exposure Limit A 15-minute TWA exposure that should not be exceeded at any time 

during a workday, even if the 8-hour TWA is within the TLV–TWA, set by 

ACGIH. 

AEGLb,c

Acute Exposure Guideline 

Level 1

AEGL-1 is the airborne concentration of a substance above which it is 

predicted that the general population, including susceptible individuals, 

could experience notable discomfort, irritation, or certain asymptomatic 

nonsensory effects. However, the effects are not disabling and are 

transient and reversible upon cessation of exposure.

Acute Exposure Guideline 

Level 2

AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a 

substance above which it is predicted that the general population, 

including susceptible individuals, could experience irreversible or other 

serious, long-lasting adverse health effects or an impaired ability to 

escape.

Acute Exposure Guideline AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a 
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Level 3 substance above which it is predicted that the general population, 

including susceptible individuals, could experience life-threatening health 

effects or death.

ERPG

Emergency Response 

Planning Guideline 1 

The maximum airborne concentration below which it is believed that 

nearly all individuals could be exposed for up to 1 hour without 

experiencing other than mild transient health effects or perceiving a 

clearly defined, objectionable odor according to AIHA. 

Emergency Response 

Planning Guideline 2 

The maximum airborne concentration below which it is believed that 

nearly all individuals could be exposed for up to 1 hour without 

experiencing or developing irreversible or other serious health effects or 

symptoms which could impair an individual's ability to take protective 

action according to AIHA.

Emergency Response 

Planning Guideline 3 

The maximum airborne concentration below which it is believed nearly 

all individuals could be exposed for up to 1 hour without experiencing or 

developing life-threatening health effects according to AIHA.

Excursion Limit d Excursion Limit Because methane (and other short-chain alkane gases through butane) 

does not have a TLV-short-term exposure limit, an excursion limit may 

be applied. Excursions in worker exposure levels may exceed 3 times 

the TLV-TWA for no more than a total of 30 minutes during a workday, 

and under no circumstances should they exceed 5 times the TLV-TWA, 

provided that the TLV-TWA is not exceeded according to ACGIH. 

IDLH Immediately Dangerous to 

Life and Health

If exposed to this concentration, room occupants are expected to be able 

to escape the room within 30 minutes without experiencing escapeimpairing or irreversible health effects.

TEELe

Temporary Emergency 

Exposure Limit 1

TEEL-1 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing other than 

mild transient adverse health effects or perceiving a clearly defined, 

objectionable odor. 

Temporary Emergency 

Exposure Limit 2

TEEL-2 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing or 

developing irreversible or other serious health effects or symptoms that 

could impair their abilities to take protective action.

Temporary Emergency 

Exposure Limit 3

TEEL-3 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing or 

developing life-threatening health effects. 

Long-Term Exposure

PEL Permissible Exposure Limit This is an 8-hour time-weighted average exposure limit set by OSHA. 

TLV-TWA Threshold Limit Value – TimeWeighted AverageThe TWA concentration for a conventional 8-hour workday and a 40-

hour workweek, to which it is believed that nearly all workers may be 

repeatedly exposed, day after day, for a working lifetime without adverse 

effect according to ACGIH. 

a All information in this table taken from EPA (1994) except where otherwise noted.

b EPA (2012)

c Applicable to emergency exposure periods ranging from 10 minutes to 8 hours.

d ACGIH (2004)

e Chemical exposure guidelines to use for emergency planning if no AEGL or ERPG is available. TEELs are developed based on concentration 

limits or toxicology parameters (DOE 2008).

According to the MSDS, exposure to propane may be hazardous if inhalation, skin contact, or eye contact 

with propane occurs. The most likely pathway of exposure is through inhalation. Propane can cause 

symptoms of asphyxiation when present in concentrations high enough to significantly lower oxygen 

concentrations below 19.5 percent by volume, such as headaches, ringing in ears, dizziness, drowsiness, 

nausea, vomiting, depression of all senses, and also unconsciousness. Under some circumstances of overexposure (i.e., oxygen levels fall below 6 percent by volume), death may occur. In addition, at high 
June 26, 2014 -- Final

8

concentrations, propane can act as a narcotic and cause central nervous system depression, including 

dizziness, drowsiness, and headaches. 

If propane is inhaled, person(s) should be immediately removed and exposed to fresh air. In accordance 

with the MSDS, EPA further recommends that if breathing is difficult, person(s) be given oxygen, 

provided a qualified operator is present, and medical attention be sought. Rescuers should not attempt to 

retrieve victims of exposure to propane without adequate PPE. At a minimum, a self-contained breathing 

apparatus (SCBA) should be worn. Exposures of propane to the skin may cause frostbite. In the case of 

dermal exposure, the MSDS for propane recommends that person(s) immediately wash the affected area 

with water and remove all contaminated clothing; if frostbite occurs, bathe (not rub) the affected area with 

lukewarm, not hot, water. If water is not available, cover the affected area with a clean, soft cloth. 

Alternatively, if the fingers or hands are frostbitten, warm the affected area by placing it in the armpit; 

gently exercise the affected part while being warmed, and seek medical attention immediately. Exposures 

of propane to the eyes could cause eye irritation. In case of ocular exposure, the MSDS for propane

recommends that person(s) immediately flush the eyes, including under the eyelids, with copious amounts 

of water for 15 minutes. 

EPA’s review of the human health impacts of this proposed substitute is contained in the public docket 

for this decision. The potential health effects of propane can be minimized by following the exposure 

guidelines and ventilation and PPE recommendations outlined in the MSDS for propane and this risk 

screen.

7. FLAMMABILITY ASSESSMENT

ASHRAE Standard 34 classifies propane as a Class A3 refrigerant. Propane is flammable when its 

concentration in air is in the range of 2.1 percent and 9.5 percent by volume (21,000 ppm to 95,000 ppm). 

In the presence of an ignition source (e.g., static electricity, a spark resulting from a switch malfunction, 

or a cigarette), an explosion or a fire could occur if the concentration of propane exceeds its lower 

flammability limit (LFL) of 21,000 ppm, posing a significant safety concern for workers and consumers if 

it is not handled carefully. The remainder of this section assesses flammability risks and summarizes the 

recommended measures to ensure safe handling and use of the refrigerant during manufacture, servicing, 

and end-use. 

7.1 Flammability Risks at Manufacture

EPA expects manufacturing to occur in a closed system and that all units are completely sealed before 

delivery and installation. If the vending machines are not charged and sealed in a closed system, EPA 

expects personnel to wear proper PPE (see Section 2) to protect themselves from releases or exposure to 

propane In addition, manufacturing facilities are anticipated to maintain proper ventilation at all times 

during the manufacture of equipment containing propane and adhere to good manufacturing practices. As 

a result, releases of propane during these manufacturing and installation operations in the presence of an 

ignition source are not anticipated. 

All propane storage and transport equipment should be installed with safety devices that minimize the 

likelihood of catastrophic releases. For example, NFPA 58 Liquefied Petroleum Gas Code (NFPA 2014) 

for liquefied propane requires the use of overfill protection devices (OPD) on cylinders to minimize the 

likelihood of leaks. The NPFA 58 Code also contains propane storage and transportation 

requirements/guidelines. Similar equipment safety and procedural requirements should be developed for 

propane and other flammable refrigerants. EPA believes that because relevant safety standards, the MSDS 

for propane, and OSHA requirements under 29 CFR 1910 (e.g., proper ventilation and storage practices 

within manufacturing facilities to prevent fire and explosion) are followed by workers, flammability 

during manufacture is not a concern. 
June 26, 2014 -- Final

9

7.2 Flammability Risk at Servicing and End-Use

The risk of flammability during servicing and end-use for the reasonable worst-case scenario and typical 

scenario (see Section 5) was investigated for propane. Both servicing and end-use of propane vending 

machines are expected to take place in the same room. In order to determine the potential flammability 

risks during servicing or end-use in case of a catastrophic release of refrigerant in an enclosed alcove (see 

Section 5), concentrations of propane immediately following a complete release of refrigerant, either 

accidental or deliberate (e.g., through vandalism or theft), were compared to the LFL for propane. The

reasonable worst-case scenario assumes an effective room size of 15 m

3

and air exchange rate of 0.5 

ACH. In this worst-case scenario, the modeling results reflect the maximum concentration in the lower 

0.4 meters of the room, as the upper portion of the room presents a much lower risk, with only 5 percent 

of the leaked refrigerant present in this area which also has a greater volume than the lower 0.4 meters of 

the room. In the typical scenario, an effective room size of 27.5 m

3

and air exchange rate of 1.5 ACH are 

assumed while the modeling results reflect the maximum concentration in the entire room, as a vertical 

concentration gradient is not assumed. Table 6 presents the results of the analysis. 

Table 6. Flammability Assessmenta

Scenario Charge Size

(g)

Effective 

Room Size 

(m3)

Vertical 

Concentration 

Gradient Height 

(m)

Maximum 

Instantaneous 

Concentration

(ppm) b,c

Reasonable Worst-Case 150 15 (530 ft3

) 0.4 30,900

Typical 150 27.5 (972 ft3

) None 2,950

Threshold Analysis 1a: Charge Size 102 15 (530 ft3

) 0.4

21,000

Threshold Analysis 1b: Charge Size 1,120 27.5 (972 ft3

) None

Threshold Analysis 2a: Room Size 150 22 (780 ft3

) 0.4

Threshold Analysis 2b: Room Size 150 3.9 (128 ft3

) None

Bold font indicates modeling results.

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.

b Lower Flammability Limit of propane is equal to 21,000 ppm.

c Values provided in these columns refer to the concentration in the lower 0.4 meters of the room, which presents the most conservative risk 

as 95 percent of the leaked refrigerant in present in this space.

In the reasonable worst-case scenario, at a charge size of 150 grams, the maximum instantaneous 

concentration of propane in the lower 0.4 meters of the room would be approximately 30,900 ppm, which 

is 150 percent of the LFL for propane (see Table 6). In the typical scenario, the maximum instantaneous 

concentration of propane in the entire room would be approximately 2,960 ppm, which is 14 percent of 

the LFL for propane. However, the accidental release of all refrigerant into the enclosed alcove is highly 

unlikely. This is because the refrigerant system is located in a protected compartment on the back side of 

the vending machine and accidents resulting in a puncture to the compressor, whether through attempted 

theft of the vending machine contents or vandalism, would be unlikely. In the case of accidental release, 

however, propane is likely to be dispersed into the air evenly and almost instantaneously upon release; the 

vending machine compressor is pressurized, which will cause propane to be released into the room 

(assumed to be at atmospheric pressure of approximately 14.7 psi) under pressure, resulting in the 

refrigerant’s quick and turbulent release, and subsequent mixing into the air. However, it is also unlikely 

that 100 percent of the refrigerant charge will be released from the system because as the refrigerant 

leaks, the system pressure will decrease and eventually equilibrate with atmospheric pressure, leaving a 

small amount of refrigerant in the system. To completely remove the entire refrigerant charge from the 

system, a vacuum pump must be used.
June 26, 2014 -- Final

10

Catastrophic releases of large quantities of refrigerant, especially in areas where refrigerant is stored, 

could cause an explosion. For the flammability threshold analysis, the conditions at which a flammability 

concern would exist (i.e., when the maximum instantaneous concentration in the lower 0.4 meters of the 

enclosed alcove equals the LFL for propane) was determined. Under the room size, ventilation rate, and 

vertical concentration gradient assumed within the reasonable worst-case scenario, the charge size of the 

propane refrigeration unit would have to be at least 102 grams for a flammability concern to exist, as 

shown in Threshold Analysis 1a. Under the room size and ventilation rate assumed within the typical 

scenario, the charge size of the propane refrigeration unit would have to be at least 1,120 grams for a 

flammability concern to exist, as shown in Threshold Analysis 1b. Using a 150-gram refrigeration unit, as 

shown under Threshold Analysis 2a and 2b, the volume of the room would have to be smaller than 22 m

3

(780 ft3) or 3.9 m

3

(138 ft3) for a flammability risk to occur under the reasonable worst-case and typical

scenarios, respectively. EPA recommends that these guidelines be followed to further minimize risk of 

flammability.

According to the results of this flammability analysis, the risk of fire is minimal if a vending machine is 

installed in a room with volumes in accordance with standards and regulations. According to ASHRAE 

Standard 34, the RCL for propane (9.5 g/m3of propane or 5,300 ppm by volume) should not be exceeded 

in any room that contains a propane vending machine. EPA recommends that in addition to the RCL, 

these guidelines be followed to further minimize risk of flammability. For this reason, it is important that 

only properly trained and certified technicians handle propane. As a further precaution, certification

requirements and training programs for technicians that handle propane should be developed using these 

guidelines. During servicing operations, technicians should ensure that proper ventilation is in place 

through the use of fans (or other mechanical ventilation devices) and portable refrigerant detectors should 

be used to alert technicians to the presence of flammable gases in the area. Vending machines should not 

be installed in small, poorly ventilated spaces such as very small enclosed areas or storage closets 

(especially as other equipment or appliances in the space would reduce the effective volume of the room).

For vending machines installed in larger areas, the risk of fire and explosion is minimal. Vending 

machines installed with propane should be clearly labeled as containing a flammable refrigerant and 

designed to prevent catastrophic leaks. The installation of leak prevention devices would further protect 

against the very limited risk of explosion. EPA believes that the risk of fire is minimal if a propane

vending machine is installed in a room with volumes and ventilation in accordance with standards, 

MSDS, and recommendations. 

8. ASPHYXIATION ASSESSMENT

The risk of asphyxiation for the reasonable worst-case scenario was investigated for propane. In this 

section, risk of asphyxiation is assessed in three ways: 1) modeling the oxygen concentration under the 

charge size and room size specified in the worst-case scenario, 2) performing a threshold analysis of 

minimum charge size needed to cause an asphyxiation risk in the room size specified in the worst-case 

scenario 3) performing a threshold analysis of the maximum room size needed to cause an asphyxiation 

risk with the charge size specified in the worst-case scenario. This analysis does not consider conditions 

that are likely to occur that would increase oxygen levels to which individuals would be exposed, such as 

open doors or windows, fans operating, conditioned airflow (either heated or cooled), or even openings at 

the bottom of doors that allow air to flow in and out. As specified in Section 5, the reasonable worst-case 

scenario in this analysis assumes a vertical concentration gradient. If the proposed substitute passes the 

screening analysis with these restrictive assumptions in place, it can be reasonably assumed that no risks 

of asphyxiation will be present under real-world conditions. The results of the asphyxiation assessment 

are summarized in Table 7 below. 
June 26, 2014 -- Final

11

Table 7. Asphyxiation Assessmenta

Scenario Charge Size (g) Effective Room 

Size (m3)

Vertical 

Concentration 

Gradient

Height (m)

Percent Oxygen 

Concentration b

Reasonable Worst-Case 150 15 (530 ft3

) 0.4 21

Typical 150 27.5 (972 ft3

) None 21

Threshold Analysis 1a: Charge Size 2,710 15 (530 ft3

) 0.4 12

Threshold Analysis 1b: Charge Size 29,800 27.5 (972 ft3

) None 12

Threshold Analysis 2a: Room Size 150 0.83 (29.3 ft3

) 0.4 12

Threshold Analysis 2a: Room Size 150 0.14 (4.9 ft3

) None 12

Bold font indicates modeling results.

s Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.

b The typical concentration of oxygen in air is considered to be 21 percent (Mackenzie & Mackenzie 1995).

In order for a risk of asphyxiation to occur, the normal concentration of oxygen in air (21 percent) in the 

lower 0.4 meters of the room must be reduced to 12 percent.6 Based on both the reasonable worst-case 

scenario and typical scenario modeling assumptions, propane in vending machines does not present a 

significant risk of asphyxiation. The concentration of propane in the air following the release of the 150-

gram charge size does not exceed 2.4 percent or 0.2 percent in the reasonable worst-case and typical 

scenarios, respectively, which has an insignificant impact on the normal concentration of oxygen in air. 

Because this modeling does not take into account any ventilation which is likely to occur, such as 

conditioned airflow, open doors, or even openings at the bottom of doors that allow air to flow in and out, 

as mentioned above, the actual asphyxiation risk to personnel is likely to be even smaller than modeled. 

For the asphyxiation threshold analyses shown in Table 7, the conditions at which an asphyxiation 

concern would exist were determined. As shown in Threshold Analysis 1a, the minimum charge of 

propane necessary to reduce the oxygen levels to 12 percent in air in the lower 0.4 meters of a room of 

volume 15 m

3

(530 ft3) was calculated to be 2,710 grams, which is more than 18 times the maximum UL 

541 charge size of 150 grams. As shown in Threshold Analysis 1b, the minimum charge of propane 

necessary to reduce the oxygen levels to 12 percent in the air of a room of volume 27.5 m3(972 ft3) was 

calculated to be 29,800 grams, which is approximately 200 times the maximum UL 541 charge size of 

150 grams. These analyses, Threshold Analysis 1a and 1b, assumed that 1) nitrogen and oxygen retain the 

same relative volumes in the rooms with the balance composed entirely of propane, and 2) the pressure of 

the room does not increase significantly with the addition of the refrigerant. As shown in Threshold 

Analysis 2a, for asphyxiation to be of concern with the proposed maximum charge size of 150 grams, in a 

15 m3room, and assuming a vertical concentration gradient height of 0.4 meters, the effective volume of 

the enclosed alcove would have to be about 0.83 m

3

(29.3 ft3) (see Table 7), which is smaller than the size 

of the vending machine itself. As shown in Threshold Analysis 2b, for asphyxiation to be of concern with 

the proposed maximum charge size of 150 grams and assuming no vertical concentration gradient in a 

27.5 m3room, the effective volume of the enclosed alcove would have to about 0.14 m3(4.9 ft3), which is 

also smaller than the size of the vending machine itself. Based on the worst-case modeling results and 

threshold analysis, EPA does not believe that the use of propane in vending machines poses a significant 

risk of asphyxiation or impaired coordination to consumers.

9. END-USE EXPOSURE ASSESSMENT

This section presents estimates of potential consumer exposures to propane and each of its impurities in 

vending machines. An exposure analysis was performed to examine potential catastrophic releases release 

 

6 Twelve percent oxygen in air is the No Observed Adverse Effect Level (NOAEL) for hypoxia (ICF 1997).
June 26, 2014 -- Final

12

of the proposed substitute under the reasonable worst-case scenario and typical scenario outlined in 

Section 5. 

For the end-use exposure assessment scenario, 30-min TWA exposures for the proposed substitute and 

each of its impurity constituents were calculated using the box model described in the Background 

Document, which was adapted to estimate concentrations on a minute-by-minute basis. The analysis was 

undertaken to determine the 30-minute TWA exposures of the proposed substitute because consumers are 

anticipated to only spend short amounts of time in the presence of vending machines while purchasing 

and consuming products. These exposures were then compared to the standard toxicity limits presented in 

Table 4 to assess the risk to end-users. However, the TWA values are fairly conservative as the analysis 

does not consider opened windows, fans operating, conditioned airflow (either heated or cooled) and 

other variables that would reduce the levels to which individuals would be exposed. Modeling was 

performed for propane and all of its impurity constituents; however, only the modeling results for propane

are presented in Table 8. As propane is approximately 99.5 percent pure, it presents the greatest risk of 

exceeding the STEL and thus is the most conservative assessment. 

Table 8. End-Use Exposure Assessmenta

Scenario Charge Size 

(g)

Effective 

Room Size 

(m3)

Ventilation 

Rate (ACH)

Vertical 

Concentration 

Gradient 

Height (m)

30-minute 

TWA End-Use 

Exposureb,c

(ppm)

Reasonable Worst-Case 150 15 (530 ft3) 0.5 0.4 27,420

Typical 150 27.5 (972 ft3) 1.5 None 2,098

Threshold Analysis 1a: Charge Size 37.7 15 (530 ft3) 0.5 0.4

6,900

Threshold Analysis 1b: Charge Size 493 27.5 (972 ft3) 1.5 None

Threshold Analysis 2a: Room Size 150 60 (2,120 ft3) 0.5 0.4

Threshold Analysis 2b: Room Size 150 8.4 (297 ft3) 1.5 None

Threshold Analysis 3a: Ventilation Rate 150 15 (530 ft3) 8.9 0.4

Threshold Analysis 3b: Ventilation Rate 150 27.5 (972 ft3) 0 None

Bold font indicates modeling results.

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.

b

30-min AEGL-1 STEL for propane is 6,900 ppm; See Table 4 for more information.

c Values provided in this column refer to the concentration in the lower 0.4 meters of the room, which presents the most conservative risk as 95 

percent of the leaked refrigerant in present in this space. 

In the reasonable worst-case scenario and typical scenario described in Section 5, catastrophic release of 

propane from a vending machine with a charge size of 150 grams was modeled. During the release event 

in the typical scenario, the modeling results indicate the maximum anticipated 30-min TWA end-use 

exposure does not exceed 30 percent of the 30-min AEGL-1 for propane. Under the plausible worst-case 

scenario, however, the 30-min AEGL-1 for propane of 6,900 ppm is likely to be exceeded (see Table 8). 

Additionally, the calculated 30-min TWA exposure also exceeds the AEGL-2 (17,000 ppm) for propane, 

but not the AEGL-3 (33,000 ppm). However, such consumer exposure is unlikely, as the reasonable 

worst-case scenario (see Section 5) assumes that 95 percent of the refrigerant is leaked into the lower 0.4 

meters of the room, where it is unlikely that persons would be contained. In addition, these modeled 

exposures were derived using conservative assumptions (e.g., minimum room volume, low ventilation 

rate [0.5 ACH], maximum charge size) that do not necessarily reflect the typical location for propane

vending machine installations (e.g., vending machines will be installed in commercial buildings, which 

have higher ventilation rates). 

Nonetheless, these potential exposures emphasize the importance associated with proper equipment 

installation (i.e. matching charge size with room dimensions). A threshold analysis was performed to 

determine the charge size, minimum room volume, and ventilation rates where vending machines 
June 26, 2014 -- Final

13

containing propane could be installed to avoid the short-term exposure limit for propane. Under the worstcase scenario in Threshold Analysis 1a, the maximum charge size that should be installed in a room of 15

m

3

(530 ft3) volume is 37.7 grams. Under the typical scenario in Threshold Analysis 1b, the maximum 

charge size that should be installed in a room of 27.5 m3(972 ft3) volume is 493 grams. If a charge size of 

150 grams is used in vending machines, the vending machines should be installed in larger spaces with 

higher ventilation rates (i.e., assuming the conditions in the reasonable worst-case scenario, vending 

machines should be installed in rooms that are at least 60 m

3

[2,120 ft3] at a ventilation rate of 0.5 ACH or 

vending machines installed in a space of 15 m

3

[530 ft3] must have a ventilation rate of at least 8.9 ACH

[see Threshold Analysis 2a and 3a]). Assuming more conservative conditions in the typical scenario in 

Threshold Analysis 2b and 3b, vending machines should be installed in rooms that are at least 8.4 m3(297 

ft3) at a ventilation rate of 1.5 ACH while vending machines installed in a large space of 27.5 m

3

(972 ft3) 

do not require ventilation. 

Because end-use exposure is only a concern under the most conservative scenario, EPA recommends 

these minimum room and ventilation rate guidelines to ensure that if a catastrophic leak of propane

occurs, it is not anticipated to result in a significant risk to consumers at end-use. To prevent exposure and 

potential serious side effects during larger releases, EPA recommends that the charge size for a propane

vending machine does not exceed the RCL (9.5 g/m3) and proposes to require compliance with UL 541 in 

any space containing a vending machine, unless proper leak protection devises are in place in order to 

prevent exposures of propane beyond the recommended limits. Additionally, these room volume and 

ventilation rate requirements simultaneously ensure that there is not a significant flammability or 

asphyxiation risk, as these requirements are more restrictive than the room sizes recommended in the 

flammability and asphyxiation assessments (see Sections 7 and 8). Proper leak protection devices and 

engineering control requirements and adherence to the MSDS will further ensure that exposure limits are 

maintained below those described in Table 8.

10. OCCUPATIONAL EXPOSURE ASSESSMENT

This section assesses potential exposures to workers during manufacture, installation, servicing, and 

disposal of propane. EPA expects that the manufacture of propane refrigerant (i.e., formulation mixing) 

and the charging of propane vending machines (i.e., receiving, blending. and filling operations) occurs in 

a closed system; all units are completely sealed before delivery and installation. As a result, exposure 

during these manufacturing and installation operations is not anticipated. 

To ensure that use of the proposed substitute in vending machines does not pose an unacceptable risk to 

workers during servicing and disposal, occupational exposure modeling was performed using a boxmodel approach. For a detailed description of the methodology used for this screening assessment, the 

reader is referred the occupational exposure and hazard analysis described in Chapter 5 of the 

Background Document. Estimates of refrigerant release per event for various release scenarios and data 

on number of events were obtained from the Vintaging Model.7For the vending machine end use,8the 

release per event was conservatively assumed to be 0.25 percent of the equipment charge during servicing

and 35 percent of the equipment charge during disposal.9 Additionally, EPA is proposing to allow 

intentional venting or release of propane as a refrigerant during installation, servicing, maintenance and 

disposal from window AC units. If venting does occur, it should be done in a well-ventilated area (e.g.,

outdoors). Therefore, scenarios in which 100 percent of the equipment charge was released during 

 

7

ICF International maintains the Vintaging Model for EPA in order to simulate the aggregate impacts of the ODS phaseout on 

the use and emissions of various ODS and their substitutes over a period of several years across 60 different end-uses. The 

model tracks the use and emissions of various compounds for the annual vintages of new equipment that enter service in each 

end-use. The vintage of each type of equipment determines such factors as leak rate, charge size, number of units in operation, 

and the initial ODS substance that the equipment contained. The service leak rate and disposal release rate assumptions are 

consistent with the small retail food refrigeration end-use in Vintaging Model version VM IO file_v4.4_11.6.12. 

8

For the purposes of this assessment, vending machines were modeled as small retail food refrigeration units.

9 During disposal it is assumed that 100 percent of the refrigerant charge remains in the unit. 
June 26, 2014 -- Final

14

servicing and disposal were also considered. The release rate per event was multiplied by the number of 

events estimated to occur over a workday. For equipment servicing, the number of events per workday 

was assumed to equal the maximum number of units anticipated to be serviced in one day (eight units) 

divided by eight hours per workday. These assumptions result in approximately 8 events per day. For

disposal, it was conservatively assumed that 10 units are disposed during an 8-hour work day. The 

modeled exposure concentrations were compared to short-term occupational exposure limits at 

installation and servicing and long-term exposure limits at disposal.

10.1 Occupational Exposure at Servicing

The potential occupational exposure during servicing was analyzed. The maximum 30-minute TWA 

exposures for propane and its impurities were estimated for the servicing exposure scenario and compared 

to their respective STELs. As summarized in Table 9, the modeling results indicate that the maximum 

anticipated occupational exposure concentrations at no point exceed 0.01 percent and 4.3 percent of the 

STEL for propane for vending machines with a 150-gram charge size for the 0.25 percent release and 100 

percent release of refrigerant during servicing, respectively. Because the exposure concentrations 

modeled under the conservative assumptions is significantly lower than the exposure limits for each 

constituent, occupational exposure to the proposed substitute during servicing is not considered a 

significant risk to workers. Further, the estimated exposures were derived using conservative 

assumptions, and represent a worst-case scenario with a low probability of occurrence. These types of 

systems are typically serviced by trained personnel using proper industrial hygiene techniques.

 

Table 9. Occupational Risk Assessment at Servicinga

Component

30-minute TWA Occupational Exposure (ppm)

Charge size: 150 grams 30-min Short Term 

Exposure Limits (ppm)

0.25% Release 100% Release

Propane 0.74 297 6,900b

Potential Impurities

Ethane 0.002 0.74 3,000c

Propylene 2 x 10-4 0.09 1,500c

n-Butane 0.001 0.23 6,900b

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.

b AEGL-1

c ACGIH (2004)

10.2 Occupational Exposure at Disposal

Disposal of propane vending machines is expected to occur with limited frequency (up to approximately 

one disposal event per day) at disposal facilities and with limited duration of exposure to the refrigerant 

charge. Potential exposures to the refrigerant during recovery and disposal are expected to occur during 

activities related to draining the refrigerant from the vending machine into cylinders (e.g., connecting of 

pipes). Such activities and related exposure is anticipated to occur within 15-30 minutes (per event/day).

Table 10 displays the maximum estimated 8-hour TWA occupational exposure levels of propane and its 

impurities during disposal. Based on the assumptions described in the beginning of Section 10, the 

modeling indicates that 8-hour worker exposure concentrations for propane and each of its impurities 

during the 35 percent release scenario and the 100 percent release scenario will at no point exceed 19

percent and 53 percent of the long-term exposure limits of any of the individual components during 

disposal of propane for vending machines with a 150-gram charge size. Table 10 displays the maximum 

estimated 8-hour TWA occupational exposure levels of propane and its potential impurities during 

disposal. Because each value is significantly lower than the exposure guidelines for each constituent, 
June 26, 2014 -- Final

15

occupational exposure to the proposed substitute during disposal does not represent a true occupational 

health hazard. Further, the estimated exposures were derived using conservative assumptions, and 

represent a worst-case scenario with a low probability of occurrence. These types of systems are typically 

disposed of by trained personnel using proper industrial hygiene techniques.

Table 10. Occupational Risk Assessment at Disposala

Component

8-Hour TWA Occupational Exposure (ppm)

Charge size: 150 grams 8-Hour Long Term 

Exposure Limits (ppm)

35% Release 100% Release

Propane 184 526 1,000b

Potential Impurities 

Ethane 0.46 1.32 1,000c

Propene 0.058 0.17 500c

n-Butane 0.14 0.40 1,000c

a Cells highlighted in green are the scenarios with exposure levels deemed to be acceptable given various 

modeling assumption options.

 

bOSHA PEL

 c ACGIH TLV 

Although anticipated occupational exposures are well below the exposure limits for each of the 

components of propane, the recommendations for proper engineering controls and PPE (e.g., safety 

glasses and gloves) in the MSDS for propane should be followed. Adequate ventilation should always be 

established during any use, handling, or storage of propane. Engineering controls should include vapor-in 

air detection systems and local exhaust ventilation during use of propane to prevent dispersion of propane

throughout the work place. In addition, an eye wash and safety shower should be near the manufacturing 

facility and locations where propane is stored and ready for use. EPA believes that if proper handling and 

disposal guidelines are followed in accordance with good industrial hygiene and manufacturing practices 

and the MSDS for propane, there is no significant risk to workers during the manufacturing, installation, 

servicing, and disposal of propane in vending machines.

11. GENERAL POPULATION EXPOSURE ASSESSMENT

Propane is not expected to cause a concern for human health in the general population when

manufactured for use and used as a refrigerant in vending machines. The proposed substitute will be 

manufactured in a closed process and is proposed for use in closed systems, and thus, significant releases 

are not anticipated. At room temperature, propane is a gas and, therefore, releases to ground or surface 

water are not anticipated, as propane is anticipated to dissipate into the atmosphere upon release to 

outside air (i.e., because natural ventilation rates would be higher and there is no enclosed space to keep 

propane concentrated). Should air releases during manufacturing operations occur, engineering controls 

should be used (e.g. carbon absorption scrubbers) to collect propane and prevent the release of propane to 

the atmosphere. EPA believes that by using proper engineering controls and by following disposal and 

containment recommendations outlined in the proposed substitute’s MSDS, exposure to propane is not 

expected to pose a significant toxicity risk to the general population.
June 26, 2014 -- Final

16

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